Home Laboratory # 4
C. Ophardt, Elmhurst College, c. 2012

ACIDS AND BASES IN RAIN, LAKES, STREAMS, AND HOUSEHOLD PRODUCTS


PART 1: PRE-LAB: Data Online (4 points)

ACID RAIN DISTRIBUTION IN THE UNITED STATES

INTRODUCTION: At an electric power plant, during the combustion reaction of coal, a small amount of sulfur in the coal is converted into sulfur dioxide or sulfur trioxide. In addition, nitrogen from the air reacts with oxygen in the high temperatures of combustion to produce nitrogen oxides. These nitrogen oxides may be formed at power plants, as well as, from automobile engines.

Acid rain may be formed from the interaction of sulfur oxides and nitrogen oxides with water to produce either sulfuric acid , H2SO4, or nitric acid, HNO3. The "acid" is measured in terms of hydrogen ions as pH. The sulfate and nitrate ions may be measured independently of each other.

As you go through this exercise it is important to understand where and how much pollution existed in 1994 the year the legislation was passed to begin lowering the concentrations through the use of the Sulfur Dioxide Cap and Trade program administered by the EPA.

The National Atmospheric Deposition Program maintains a series of monitoring stations to measure acid rain and other associated ions. The www address is: http://nadp.sws.uiuc.edu/

A series of colored contour maps which give a visual picture of the distribution and concentration of various ions is available in the form of Isopleth Maps.



QUES. 1: First do a little general survey to try several years like - pH 1994 map, then pH 2009 map,

and finally pH 2002 map to answer the question.  Which general areas or states of the country have the lowest pH values recorded? What is the lowest pH and its location? Use 2002 Field pH data to answer the question below.

a. Ohio, pH 4.1 b. Pennsylvania, pH 4.4, c. New York, pH 4.3



QUES. 2:
First do a little general survey to try several years like - sulfate concentration map 1994, then sulfate concentration map 2009,

and finally sulfate concentration map 2002 to answer the question.  Which general areas or states of the country have the highest concentration of sulfate ion (SO4-) values recorded? What is the highest sulfate ion concentration and its location?  Use the 2002 SO4 data to answer the question below.

a. New York, sulfate = 2.2 b. Pennsylvania, sulfate = 2.1 c. Ohio, sulfate = 2.7


QUES. 3: First do a little general survey to try several years like - nitrate concentration map 1994, then nitrate concentration map 2009,

and finally nitrate concentration map 2002 to answer the question.Which general areas or states of the country have the highest concentration of nitrate ion (NO3-) values recorded? What is the highest nitrate ion concentration and its location?  Use the 2002 NO3 date to answer the question below.

a. Ohio, nitrate = 1.9 b. Michigan, nitrate = 2.2 c. New York, nitrate = 2.4


4. Correlation of pH, sulfate ions, and nitrate ions:

QUES. 4:
Which general areas or states of the country have the highest presence of mostly coal fired power plants?  The link provides the CO2 emissions which are directly related to the location of coal fired plants.

see: Power plant locations by state graphed by Carbon dioxide emissions

a. Western States b. Central to eastern Midwest  (Illinois, Indiana, Ohio, Kentucky) c. Northeast ( NY, Vermont, N.H., Maine, Mass.)

QUES. 5: What is the correlation between the low pH, high concentration of sulfate and nitrate ions and the emission of sulfur dioxide and nitrogen oxides from the coal fired power plants and wind direction(what is the prevailing wind pattern for the US? Do the winds and weather move from the west to the east or in the reverse direction?)?  For your answer concentrate more on the eastern half of the country.  In a correlation you need to include all of the factors mentioned in your answer.  A correlation is the interrelationships of all of the data.  For example correlate pH to location of power plants to wind patterns.  Do the same for sulfate and nitrate.

Use info from Ques. 1-3 and locations of power plants from Ques. 4

QUES. 6: What is the correlation of acid rain deposition and senstive areas of surface waters which are most effected by the acid rain.? Just looking for general areas of the country - please ignore the northwest.  In a correlation you need to include all of the factors mentioned in your answer.  A correlation is the interrelationships of all of the data.

see:
Map of Ecologically Sensitive Areas

5. Trends in acid rain pollutants: The United States Geological Survey is responsible for monitoring the trends in acid rain and other ions as a result of the implementation of the Clean Air Act which calls for the reduction in sulfur dioxide emissions. A detailed report and several graphics may be analyzed for information regarding the benefits of the first phase of sulfur dioxide emissions.

QUES. 7: Analyze the maps and draw conclusions about whether these results show less, more, or no change in concentrations for each of the two chemicals listed below i.e. are acid rain pollutants getting worse or better:

a. What has been the sulfate concentration changes over the last 15 years?  Use the maps from Ques. 2
Or also check out Animated Sulfate concentration maps.  This may not open directly in the browser but should open from your download window.

b. What has been the nitrate concentration changes
over the last 15 years?  Use the maps from Ques. 3 This is the next challenge to reduce these emissions even more.  

Or also check out Animated Nitrate concentration maps. This may not open directly in the browser but should open from your download window.




INTRODUCTION TO LABORATORY:

The concept of pH is important in the study of chemistry. The pH of a substance indicates whether a substance is acidic or basic (alkaline). The pH is measured on a numerical scale from 0 to 14, with pH 0 being very acidic, pH 7 as neutral, and pH 14 as very basic. One other important feature of the pH scale is that a difference of one pH unit means a 10 times change in relative acidity. For example a pH of 1 is 10 times more acidic than a pH 2.

CONCEPTS:
An acid contains hydrogen ions (H+) and a base contains hydroxide ions (OH-). As pH numbers decrease, the acidity increases (the amount of hydrogen ions increase. As pH numbers increase it becomes more basic (the amount of hydroxide ions increase).

Indicators are dyes that are used to test the pH of a substance. They work on the principle that at one pH the dye is one color, but at a different pH the dye is a different color. There are many synthetic and natural dyes that behave as acid/base indicators. Blue Litmus paper is saturated with a dye that turns red in the presence of acid. Red Litmus paper turns blue in the presence of a base. In this lab, various indicators are impregnated into the paper strip and give a variety of colors depending upon the pH of the sample.

 

PART 2: Online Computer Lab (4 points)

SOLUTIONS OF ACIDS AND NEUTRALIZATION - SIMULATION OF ACID RAIN IN LAKES.

****All Data for Part 2 is given online****
****You do not actually have to complete these procedures. Dr. Ophardt did them for you and took pictures of the results. You should read the procedures to see what was done, record the data, and answer the questions.*****

PROCEDURE 1. SOLUTIONS OF VINEGAR - DILUTED TO THE CONCENTRATION OF ACID RAIN

Vinegar from the grocery store contains 5 % acidity in the form of acetic acid. This will be used to simulate the acid rain. The pure tap water simulates a granite lake in the Northeast U.S. with relatively pure water . If you do not have a quart jars handy, you may substitute a liter pop bottle or large bowls of similar size.



Solution # 1: Put ONE cup of vinegar into a quart jar and fill the jar to the top with water. Mix well with a spoon.
Solution # 2: Take ONE tablespoon of Solution # 1 and put it into a second quart jar. Fill this jar to the top with water and mix well.

Solution # 3: Take ONE tablespoon of Solution # 2 and put it into a third quart jar. Fill this jar to the top with water and mix well. This jar Simulates acid rain, which has a concentration of acid somewhere near that of Solution # 3.

Cup # 4: Fill a cup about 3/4 with pure vinegar.

Cup # 5: Fill a cup about 3/4 with pure tap water. (Simulates a granite rock lake)

ProfONotes: Graphic for Procedure 1


PROCEDURE 2. NEUTRALIZATION OF ACIDS WITH BASE (TUMS)

The stomach antacid, TUMS, contains the base, calcium carbonate, CaCO3, Calcium carbonate is the same compound that is present in limestone rock. In some soils and lakes, limestone is present to neutralize the acid snow or rain. In this experiment, you will try to determine whether varying amounts of acid are neutralized by a constant amount of base. The hydrogen ions in the acid are ultimately converted into water molecules by the neutralization reaction.
The reaction is: CaCO3 + HC2H3O2 ---> CO2 gas + H2O + Ca(C2H3O2)2

ProfO Notes: Acid plus carbonate graphic

ProfO Notes: Carbon dioxide gas evolution graphic
ProfO Notes: pH of TUMS

CONCEPTS:

If the acid is in greater amount, the pH will be less than 7 and the acid will not be completely neutralized.
If the base is in greater amount, the pH will be greater than 7 and the acid will be neutralized.

Procedure:

1. Set up five cups and label them with the appropriate numbers.

2. Measure one cup of liquid from Solution # 1 and pour it into cup # 1T.

3. Measure one cup of liquid from Solution # 2 and pour it into cup # 2T.

4. Continue in the same manner for Solution # 3T.

5. Measure about 3/4 cup of pure vinegar into cup # 4T. (This is in addition to the one previously done.)

6. Put about 3/4 cup of tap water in cup # 5T. (This is in addition to the one previously done.)(Simulates an alkaline or a buffered lake)

7. Put ONE TUM tablet into each cup. (cup # _ T = cup with Tums tablet)

8. After the TUM tablet has soaked in the solution for a couple of minutes, use a spoon to crush the tablet. Stir the solution well every couple of minutes. The tablet may not completely dissolve.

9. After 8-10 minutes or more minutes, the solutions are ready for the pH measurement as indicated in PROC. 3.



PROCEDURE 3: MEASUREMENT OF THE PH OF SOLUTIONS

****All Data for Procedure 3 is given online****
****You do not actually have to complete these procedures. Dr. Ophardt did them for you and took pictures of the results. You should read the procedures to see what was done, record the data, and answer the questions.*****

The pH paper in the glass tube is called wide range pH paper (pH WR).
The pH paper in the packet labele rain survey is called narrow range pH paper (pH NR)

1. Use the wide range pH paper (pH WR ) to measure the pH of all of the pure, original solutions 1-5 (without the TUM tablet). Dip a small piece of the pH paper into the solutions and compare the color to the standard color chart to find the pH value. Record color and pH in the Data Table.


2. Again use the wide range pH paper (pH WR ) to measure the pH of all of the solutions (cups # 1-5 T) with the TUM tablet. Dip a small piece of the pH paper into the solutions and compare the color to the standard color chart to find the pH value. Record color and pH in the Data Table.

Data Table

 

 pure solution
    solutions with TUM tablet
   color  pH WR   color   pH WR
 Solution # 1        
 Solution # 2        
 Solution # 3        
Pure Vinegar #4        
Tap water # 5        




QUES. 8:
Which pure solution has the most acid present?

a. 1 b. 2 c. 3 d. 4 e. 5

Ques. 9: Which pure solution has the least acid after the dilutions?

a. 1 b. 2 c. 3

QUES. 10: What is the property of the TUM tablet?

a. provides an acid b. provides a base c. can not really tell

QUES. 11: Which solutions with the TUM tablet still has most acid? This solution is not neutralized by the base in TUMS.

a. 1 b. 2 c. 3 d. 4 e. 5


QUES. 12: Which acidic solution with the TUM tablet has been neutralized the most?

Hint: Look for some slight differences between the pure acid and the acid that has reacted with the TUMS. Look for the direction of the pH change. Has the pH increased which means that there is less acid present? The pH may not quite reach 7 under these conditions.

a. 1 b. 2 c. 3

QUES. 13: Which solution has the most the base from the TUMS tablet?

a. 1 b. 2 c. 3 d. 4 e. 5

QUES. 14: a. Comment on the reasons for why some samples are neutralized by the TUMS.

14b. Why are some of the solutions not neutralized very well by the TUMS.


PART 3. At home collection of lab data (9 points total (3 for each procedure))

PH OF RAIN AND OTHER NATURAL WATER SAMPLES

INTRODUCTION:

Natural "clean" water from melted snow or rain water has a normal pH of 5.6-5.2. This natural "clean" rain water may be found in only a few remote areas in the world. You might expect that "clean" rain water would have a pH of 7. The reason that it is not pH of 7, is that carbon dioxide from the air reacts with the water droplets to form carbonic acid. Carbonic acid in rain water gives a pH of about 5.6. Carbonic acid is normally found in many carbonated drinks.

Acid snow or acid rain may contain additional acids in the form of sulfuric acid and nitric acid.

Sulfuric acid is formed by the reaction of sulfur trioxide with the water droplets. Sulfur trioxide is formed from sulfur dioxide, which is formed when coal containing sulfur is burned at an electric power plant.

Nitric oxide is formed during any combustion reaction at high temperatures such as during the burning of coal or in an automobile engine. The nitric oxide reacts with oxygen to form nitrogen dioxide, which in turn reacts with water droplets to form nitric acid.


Procedure 1: Collection of snow, rain, or other types of water (3 points)

The goal will be to collect a total (from a. or b. below) of 6 different samples - a. several rain events and/or b. other natural water sources such as lake, pond, river, tap, or bottled water.

For full credit a total of 6 samples are needed (3 points). Only 4 samples = 2points; only 2 samples = 1 point.

a. Rain or Snow Samples:

1. In order to collect the rain, snow, or dew at the time of the event, you will need a clean glass or cup. Carefully clean the collection containers to be used. If detergents are used, thoroughly rinse the container with lots of tap water.

2. Choose a location that is away from trees and buildings. Leave the collection container outside for the duration of the snow or rain event. As a variable, you may find different results if you collect a rain sample immediately (within the first half hour) and again later in the rain event.

3. If the snow is already on the ground, and is sufficiently deep and away from trees, scoop some snow into the container. Take the collection container inside, if snow is present, let it melt.

4. As soon as possible after collecting the sample, use both the wide range and narrow range pH paper to measure the pH of the sample and record the results - paper color and pH number in in the data table in Ques. 15.

Lake, River, Pond, Tap or Bottled Water:

5. Follow #1 above for the collection container. Being careful not to fall into the water, collect a grab sample from the appropriate body of water.

6. Be sure to wash your hands thoroughly after collecting a polluted water source.

 

 Note: Do not be too surprised if your samples do not show very low values in pH, like pH = 4. In some cases, there are substances in the air that are bases and these may neutralize the acids present. In other cases, using the pH paper is a relatively "crude" measuring device, but the best we have for home use.

 

DATA TABLE.

QUES. 15a. DATA TABLE: Record paper color and pH. Record significant information about the sample collection process: date, time, details of the sample location area, and any other information that may be important.

15b: Discuss any significant findings, insights, and surprises about the pH of various samples.

Procedure 2: ACID-BASE PROPERTIES OF HOUSEHOLD PRODUCTS (3 points)

What is the pH of a number of household products? Are they acids, bases, or neutral compounds?

HOUSEHOLD PRODUCTS:
Use any or all of the following including others that you may have available. The assignment is to test at least 6 different substances for full credit. Vinegar, ammonia, window cleaner, lemon juice, various detergents, oven cleaner, toilet bowl cleaner, baking soda, baking powder, stomach antacids, Alka Seltzer, etc.
For full credit (3 points). Only 4 samples = 2points; only 2 samples = 1 point.

1. For as many household products as available, add 1/4 or less teaspoon of solid into a cup. For those products that are already liquids, cover the bottom of the cup with liquid. Then fill the cup 1/4 with water.

2. Use the wide range pH paper and dip a small piece into each solution. Make a Data Table and record the color and matching pH observed.


QUES. 16a. DATA TABLE: Record name of substance, paper color, pH , and whether each product is acidic, basic, or neutral.

16b: Discuss any significant findings, insights, and surprises about the pH of various samples.



Procedure 3:"ACID RAIN" NEUTRALIZATION BY ALKALINITY IN LAKES (3points)

Most soils contain substances which may effect the pH of the water that comes into contact with it. A soil may or may not have basic properties which will neutralize "acid" rain or snow. Many lakes with surrounding bedrock of limestone have carbonate or bicarbonate as a base to make the lake somewhat alkaline. The amount of carbonates which are present is sometimes referred to as the buffering capacity or the acid neutralizing capacity; the more carbonate present the greater the buffering capacity or the greater acid neutralizing capacity.

This property was simulated by two different "lakes"; one "lake" containing tap water alone and the second "lake" containing the TUM tablet - calcium carbonate. Many lakes in the Northeast region of the United States, have a granite bedrock which provides very little buffering capacity. This was simulated with the tap water. The lakes in the Midwest and West have soils and bedrock which contain limestone, calcium carbonate - simulated with the TUM tablet in water.

Tap Water "Lake"

1. Fill a cup about 3/4 with pure tap water. (Simulates a granite rock lake)

2. Use the eye dropper to add 20 drops of pure vinegar (simulated acid rain) to water in the cup of pure tap water without the TUMS tablet (simulated lake). Stir and mix well. Again measure the pH. (It might be 4 or 5) Record the results in the DATA TABLE which follows.

3. Again add one dropperful of vinegar (squeeze bulb - whatever vinegar is drawn in is a dropperful). Stir well and measure the pH.

4. Repeat step 3 one more time.

Alkaline "Lake" with TUMS tablet

5. Put about 3/4 cup of tap water into a second cup. Put ONE TUM tablet into this cup. After the TUM tablet has soaked in the solution for a couple of minutes, use a spoon to crush the tablet. Stir the solution well every couple of minutes. The tablet may not completely dissolve. (Simulates an alkaline or a buffered lake)

6. Use the eye dropper to add 20 drops of pure vinegar (simulated acid rain) to water in the cup with the TUMS tablet (simulated alkaline lake). Stir and mix well. Again measure the pH. (It might be 6 or 7) Record the results in the DATA TABLE which follows.

7. Again add one dropperful of vinegar (squeeze bulb - whatever vinegar is drawn in is a dropperful). Stir well and measure the pH.

8. Repeat step 7 one more time.

QUES. 17: DATA TABLE

 

Tap Water - "granite lake"
pure water

   "Alkaline lake"
water plus TUMS tablet
   color  pH WR  color   pH WR
20 drops vinegar        
 1 dropperful        
 2 dropperful        




The acid rain neutralization with sulfuric acid and calcium carbonate, CaCO3, shows the neutralization reaction to make calcium sulfate, CaSO4, and carbonic acid.

H2SO4 + CaCO3 -----> CaSO4 + H2CO3

The carbonic acid is reacting further to make bubbles of carbon dioxide which appear in the solution.

The reaction with vinegar, acetic acid, is very similar.

QUES. 18: a. Explain the differences in the two results for the two types of "lakes" in terms of the acid neutralizing capacity. Why does it take more vinegar to reach a lower pH in the alkaline "lake"?

18b. What are the implications of these results for the lakes in the Northeast which do not have very much calcium carbonate present, but which are receiving the most of the acid rain? Are they going to turn into "acid" lakes or will they be able to neutralize the acid rain?